This is a really well presented and informative article for Mac users considering basic X10 home automation - probably the best I've found.

Aside from the excellent home automation examples you've explained - I'm also curious to learn how to set up a simple security and monitoring system for the home that can let me know whether somebody has tried to enter our house while we're away on vacation or at the office. I'm sure it's possible. One could use an old computer as the server for internet access.